1. Field of the Invention
The invention relates to a method for adjusting an optical axis of an optical disc drive; in particular, to an adjusting method that can assist the optical disc drive in more accurately obtaining the data of an optical disc disposed thereon.
2. Description of the Related Art
Optical disc drives use light to transform information stored on an optical disc to a machine-readable format, e.g., binary data. Examples of optical disc drives are known in the art as compact disc drives (often referred to simply as CDs) and digital versatile disc drives (often referred to simply as DVDs). Some optical disc drives have the additional capability of being able to write data onto an optical disc by the use of a light source, e.g., a laser. Optical disc drives are used in various applications including music and video playing and recording devices and computer data storage devices.
When the data of an optical disc is obtained by the optical disc drive, an RF signal jitter transmitted from an optical pickup of the optical disc drive is proportional with an error rate. That is, when the jitter is greater, the error rate is also greater. Furthermore, when the jitter becomes too great, the data of the optical disc cannot be obtained by the optical disc drive. If the optical quality of the laser light, reflected to the optical pickup from the optical disc, is enhanced, the RF signal jitter can be inhibited. One manner of enhancing the optical quality is to allow the optical axis of the optical pickup (the laser light path emitted from the optical pickup) to be normal with the surface of the optical disc. Thus, the refractive loss and the diffusive loss of the laser light are decreased during reflection. As a result, in a conventional optical disc drive, a mechanism for adjusting its turntable or its guide bar is additionally disposed. Thus, a plane formed by the turntable or the guide bar can be adjusted to compensate the assembly error and the error of the optical axis of the optical pickup. Especially for DVDs, the effect of RF signal jitter due to the error of the optical disc drive is more apparent than that of CDs. Thus, the adjusting mechanism has become standard equipment in DVD players.
In a conventional process for manufacturing the optical disc drive, the optimal adjustment of the adjusting mechanism is determined based on the error rate or the value of the RF signal jitter obtained from the test disc. During adjustment, the lowest value of the error rate or the RF signal jitter is the optimal adjustment. However, among the factors that influence the error rate or the RF signal jitter, there are many factors other than the degree of inclination of the optical axis of the optical pickup, such as the quality of the optical disc or circuit noise. That is, the amount of inclination of the optical axis of the optical pickup is not the only factor. Thus, in the conventional adjusting process, the optimal adjustment is the optimal adjustment of the test disc, but not the optical axis of the optical pickup itself. That is, if the test disc is changed to retest the same optical disc drive, the position of the optimal adjustment is also changed. Furthermore, since the factors influencing the error rate and the RF signal jitter are complicated, the lowest value is difficult to judge. Thus, the optimal adjustment is also difficult to judge, and the time required for adjustment increases. As a result, the adjustment causes a bottleneck, and enhanced throughput is difficult to achieve.